As is known, timely revealing of hypovolemia can be advantageous in numerous therapeutic or pre-therapeutic contexts.
In a non-limiting way, it is for example important to determine an eventual onset of internal haemorrhaging, in order to be able to intervene rapidly and in good time such as to prevent damage which can, in the worst cases, even lead to decease of a patient.
Identifying hypovolemy conditions is however not easy to do. In particular, the early identification of haemorrhages, while avoiding using invasive systems internal of the human body, is particularly complex as the site where the haemorrhage occurs is not evident by inspection of external tissues of the patient.
In the past research has been made into the analysis of various parameters with the aim of arriving at a verification of haemorrhage conditions which do not require access to the inside of the human body.
In particular the publication “Changes in left ventricular ejection time and pulse transit time derived from finger photoplethysmogram and electrocardiogram during moderate haemorrhage”—Clin Physiol Funct Imaging (2009)-29, pages 163-169, authors Paul M. Middelton et al., discusses the analysis of various parameters with the aim of verifying the existence of relations between haemorrhages induced by donation on donor subjects and certain signals detected in the donor.
In particular, the above publication uses the signal produced by an echo-cardiograph as well as the signal produced by a pulse oximeter in order to determine parameters such as: the interval RRi between successive R wave peaks, the PTT, the pulse transit time, LVET corresponding to the interval between onset and end of ventricular ejection time, the RRi gradient, the PPT gradient, the LVET gradient.
Although the document in question discusses how the presence of a haemorrhage can influence these parameters, not correlation is established among the various parameters, nor is any indication given for the practical and efficient determination of haemorrhage conditions, or more in general conditions of hypovolemia.